The present invention relates to a pressure control installation for the pressure of the drawing apparatus, of the ram mass balance, of the workpiece ejection units or similar pressure loads in presses. These presses generally include pressure producing, pressure storing, and pressure sensing means; a pressure regulating unit consisting of a control unit for the pressure predetermination, of a pressure comparing device and of a valve unit for the adjustment of the necessary pressure, and memory means for storing and readying the optimized pressure values.
The individual pressure consuming stations of a press, gang press or multi-stage press as well as presses of a press line must be actuated at least in part with greatly varying high pressures. It is necessary during the installation of a press to render the values established during the optimization and interim values readable or fetchable and to display these values to the operator during interim periods.
An installation of the aforementioned type is described in the U.S. Pat. No. 3,945,230 in which variables of a press are adjusted during the change of the work tool by way of a pressure regulating installation. The pressure loads are connected to a pressure reservoir whose pressure values are regulatable by way of a comparison arrangement. A voltage-controlled pressure regulating valve unit is installed in the pressure line leading from the pressure producer to the pressure reservoir for the pressure build-up in case of excessively low pressure values and for the pressure reduction in case of excessively high pressure values in the pressure reservoir. For that purpose, the pressure in the pressure reservoir is read-out by way of a pressure sensor. The actual signal is compared in a voltage comparator element with the desired predetermination value of a pressure. The difference signal present at the valve unit as signal for the pressure formation.
The aforementioned printed publication discloses a logic arrangement, by means of which it is possible to adjust initial conditions of the press and to control the adjusted values, however, without describing in detail the logic arrangement. The press adjustment takes place automatically according to a program, once the values are set or adjusted. However, the aforementioned prior publication does not teach possibilities for matching several pressure loads to be acted upon with different pressure, the elimination of the difficulties of the press installation which occur to an increasing extent as a result thereof, the avoidance of the difficulties by a corresponding circuit structure as well as possibilities for the acceptance and re-use of the optimized values determined in the teach-in-operation.
In contradistinction thereto, it is the object of the present invention to considerably improve, for the operator, the setting-up or installing phases prior to and during the teach-in operation and to open up to the operator possibilities of a simple control of the running-in operation and the use of these data for subsequent applications. Additionally, new circuit techniques are to be used according to the present invention and new circuit components are to be used for a new setting-up or installing operation of the press.
The underlying problems are solved according to the present invention by a number of pressure regulating units required in dependence on different pressures, by a stored programmable control (SPS) for the control of the data traffic, to which the pressure regulating units are connected by way of selection circuits (interfaces), by memory means connected bus-like to the stored programmable control for the program input, the program change, and for the data storage, and by further manual numerical input means for the coded input of program-changing, pressure-changing data representing program-values, actual values as well as desired values which are adapted to be read-out and/or inputted.
According to a further feature of the present invention, the data traffic according to the present invention takes place by the addressing possibility by means of a selection circuit constructed as multiplexer for the data transfer between the regulators and the stored programmable control for the individual call-up of each individual regulator. As a result thereof, the pre-requisites for the individual call-up of each regulator and for a considerable reduction of the lines leading from the interface to the stored programmable control and to the further peripheral units are achieved.
Beyond the aimed-at and therewith reliable call-up or read-out of the actual value of the individual pressure regulating units, the present invention provides a pressure control system, by means of which the response to predetermined respectively predeterminable operating steps are realized and input errors and storage errors are avoided. This is achieved in a preferred embodiment of the present invention by a routine in the stored programmable control unit activatable, by a manually triggerable data transfer key. With an actuated data transfer key; the existing actual values from the individual pressure regulating units are individually called or fetched, and stored in memories and are transferred to the visual representation means. The operator therefore has the possibility of access and change of the data on the basis of predetermined input steps.